Best-fit parameters vs. input parameters for the case of a 0.1 mCrab source observed for a 150 ks X-IFU observation (configuration 4, R_f = 2, A_Fe = 2). Fifty spins are generated with a constant spacing between 0 and 0.995. The other parameters are allowed to vary with the range listed in Table 1. Left: black hole spin. Right: height of irradiating source against input values. Errors are computed at the 90% confidence level for variation of one single parameter. The mean errors on the spin and height of the irradiating source are ∼0.17 and ∼0.6 R_g respectively. The errors on all parameters are listed in Table 2.